1 /* 2 * This file is subject to the terms and conditions of the GNU General Public 3 * License. See the file "COPYING" in the main directory of this archive 4 * for more details. 5 * 6 * Copyright (C) 1995 - 2000 by Ralf Baechle 7 */ 8 #include <linux/signal.h> 9 #include <linux/sched.h> 10 #include <linux/interrupt.h> 11 #include <linux/kernel.h> 12 #include <linux/errno.h> 13 #include <linux/string.h> 14 #include <linux/types.h> 15 #include <linux/ptrace.h> 16 #include <linux/mman.h> 17 #include <linux/mm.h> 18 #include <linux/smp.h> 19 #include <linux/vt_kern.h> /* For unblank_screen() */ 20 #include <linux/module.h> 21 22 #include <asm/branch.h> 23 #include <asm/mmu_context.h> 24 #include <asm/system.h> 25 #include <asm/uaccess.h> 26 #include <asm/ptrace.h> 27 #include <asm/highmem.h> /* For VMALLOC_END */ 28 29 /* 30 * This routine handles page faults. It determines the address, 31 * and the problem, and then passes it off to one of the appropriate 32 * routines. 33 */ 34 asmlinkage void do_page_fault(struct pt_regs *regs, unsigned long write, 35 unsigned long address) 36 { 37 struct vm_area_struct * vma = NULL; 38 struct task_struct *tsk = current; 39 struct mm_struct *mm = tsk->mm; 40 const int field = sizeof(unsigned long) * 2; 41 siginfo_t info; 42 43 #if 0 44 printk("Cpu%d[%s:%d:%0*lx:%ld:%0*lx]\n", raw_smp_processor_id(), 45 current->comm, current->pid, field, address, write, 46 field, regs->cp0_epc); 47 #endif 48 49 info.si_code = SEGV_MAPERR; 50 51 /* 52 * We fault-in kernel-space virtual memory on-demand. The 53 * 'reference' page table is init_mm.pgd. 54 * 55 * NOTE! We MUST NOT take any locks for this case. We may 56 * be in an interrupt or a critical region, and should 57 * only copy the information from the master page table, 58 * nothing more. 59 */ 60 if (unlikely(address >= VMALLOC_START && address <= VMALLOC_END)) 61 goto vmalloc_fault; 62 #ifdef MODULE_START 63 if (unlikely(address >= MODULE_START && address < MODULE_END)) 64 goto vmalloc_fault; 65 #endif 66 67 /* 68 * If we're in an interrupt or have no user 69 * context, we must not take the fault.. 70 */ 71 if (in_atomic() || !mm) 72 goto bad_area_nosemaphore; 73 74 down_read(&mm->mmap_sem); 75 vma = find_vma(mm, address); 76 if (!vma) 77 goto bad_area; 78 if (vma->vm_start <= address) 79 goto good_area; 80 if (!(vma->vm_flags & VM_GROWSDOWN)) 81 goto bad_area; 82 if (expand_stack(vma, address)) 83 goto bad_area; 84 /* 85 * Ok, we have a good vm_area for this memory access, so 86 * we can handle it.. 87 */ 88 good_area: 89 info.si_code = SEGV_ACCERR; 90 91 if (write) { 92 if (!(vma->vm_flags & VM_WRITE)) 93 goto bad_area; 94 } else { 95 if (!(vma->vm_flags & (VM_READ | VM_WRITE | VM_EXEC))) 96 goto bad_area; 97 } 98 99 survive: 100 /* 101 * If for any reason at all we couldn't handle the fault, 102 * make sure we exit gracefully rather than endlessly redo 103 * the fault. 104 */ 105 switch (handle_mm_fault(mm, vma, address, write)) { 106 case VM_FAULT_MINOR: 107 tsk->min_flt++; 108 break; 109 case VM_FAULT_MAJOR: 110 tsk->maj_flt++; 111 break; 112 case VM_FAULT_SIGBUS: 113 goto do_sigbus; 114 case VM_FAULT_OOM: 115 goto out_of_memory; 116 default: 117 BUG(); 118 } 119 120 up_read(&mm->mmap_sem); 121 return; 122 123 /* 124 * Something tried to access memory that isn't in our memory map.. 125 * Fix it, but check if it's kernel or user first.. 126 */ 127 bad_area: 128 up_read(&mm->mmap_sem); 129 130 bad_area_nosemaphore: 131 /* User mode accesses just cause a SIGSEGV */ 132 if (user_mode(regs)) { 133 tsk->thread.cp0_badvaddr = address; 134 tsk->thread.error_code = write; 135 #if 0 136 printk("do_page_fault() #2: sending SIGSEGV to %s for " 137 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 138 tsk->comm, 139 write ? "write access to" : "read access from", 140 field, address, 141 field, (unsigned long) regs->cp0_epc, 142 field, (unsigned long) regs->regs[31]); 143 #endif 144 info.si_signo = SIGSEGV; 145 info.si_errno = 0; 146 /* info.si_code has been set above */ 147 info.si_addr = (void __user *) address; 148 force_sig_info(SIGSEGV, &info, tsk); 149 return; 150 } 151 152 no_context: 153 /* Are we prepared to handle this kernel fault? */ 154 if (fixup_exception(regs)) { 155 current->thread.cp0_baduaddr = address; 156 return; 157 } 158 159 /* 160 * Oops. The kernel tried to access some bad page. We'll have to 161 * terminate things with extreme prejudice. 162 */ 163 bust_spinlocks(1); 164 165 printk(KERN_ALERT "CPU %d Unable to handle kernel paging request at " 166 "virtual address %0*lx, epc == %0*lx, ra == %0*lx\n", 167 raw_smp_processor_id(), field, address, field, regs->cp0_epc, 168 field, regs->regs[31]); 169 die("Oops", regs); 170 171 /* 172 * We ran out of memory, or some other thing happened to us that made 173 * us unable to handle the page fault gracefully. 174 */ 175 out_of_memory: 176 up_read(&mm->mmap_sem); 177 if (is_init(tsk)) { 178 yield(); 179 down_read(&mm->mmap_sem); 180 goto survive; 181 } 182 printk("VM: killing process %s\n", tsk->comm); 183 if (user_mode(regs)) 184 do_exit(SIGKILL); 185 goto no_context; 186 187 do_sigbus: 188 up_read(&mm->mmap_sem); 189 190 /* Kernel mode? Handle exceptions or die */ 191 if (!user_mode(regs)) 192 goto no_context; 193 else 194 /* 195 * Send a sigbus, regardless of whether we were in kernel 196 * or user mode. 197 */ 198 #if 0 199 printk("do_page_fault() #3: sending SIGBUS to %s for " 200 "invalid %s\n%0*lx (epc == %0*lx, ra == %0*lx)\n", 201 tsk->comm, 202 write ? "write access to" : "read access from", 203 field, address, 204 field, (unsigned long) regs->cp0_epc, 205 field, (unsigned long) regs->regs[31]); 206 #endif 207 tsk->thread.cp0_badvaddr = address; 208 info.si_signo = SIGBUS; 209 info.si_errno = 0; 210 info.si_code = BUS_ADRERR; 211 info.si_addr = (void __user *) address; 212 force_sig_info(SIGBUS, &info, tsk); 213 214 return; 215 vmalloc_fault: 216 { 217 /* 218 * Synchronize this task's top level page-table 219 * with the 'reference' page table. 220 * 221 * Do _not_ use "tsk" here. We might be inside 222 * an interrupt in the middle of a task switch.. 223 */ 224 int offset = __pgd_offset(address); 225 pgd_t *pgd, *pgd_k; 226 pud_t *pud, *pud_k; 227 pmd_t *pmd, *pmd_k; 228 pte_t *pte_k; 229 230 pgd = (pgd_t *) pgd_current[raw_smp_processor_id()] + offset; 231 pgd_k = init_mm.pgd + offset; 232 233 if (!pgd_present(*pgd_k)) 234 goto no_context; 235 set_pgd(pgd, *pgd_k); 236 237 pud = pud_offset(pgd, address); 238 pud_k = pud_offset(pgd_k, address); 239 if (!pud_present(*pud_k)) 240 goto no_context; 241 242 pmd = pmd_offset(pud, address); 243 pmd_k = pmd_offset(pud_k, address); 244 if (!pmd_present(*pmd_k)) 245 goto no_context; 246 set_pmd(pmd, *pmd_k); 247 248 pte_k = pte_offset_kernel(pmd_k, address); 249 if (!pte_present(*pte_k)) 250 goto no_context; 251 return; 252 } 253 } 254